1. Field of the Invention
The present invention relates to a three-dimensional (3-D) coordinate measuring method and a 3-D coordinate measuring apparatus for measuring 3-D coordinates of large structures, such as ships, bridges, civil works, buildings, and components therefor. In addition, the present invention relates to a building method employing the aforementioned 3-D coordinate measuring method and apparatus.
2. Description of Related Arts
Generally, a two-dimensional (2-D) measuring apparatus using, for example, a transit, a measuring tape, and a plumb bob, is employed to measure large structures such as ships, bridges, civil works, and buildings. In recent years, however, such measurement is carried out using a trigonometrical survey developed in the field of measurement. Also used for the measurement is a 3-D measuring apparatus that includes a measuring apparatus with an electrooptical distance-measuring device according to distance-measuring and angle-measuring schemes.
For example, a brand xe2x80x9cMONMOSxe2x80x9d is commercially marketed by Sokkia Co., Ltd. This brand is a 3-D coordinate measuring system in which an arbitrary point of a measurement target object (or, a measurement target substance) can be measured with a single measuring apparatus. In this system, arbitrary two points are preliminarily measured, and a 3-D coordinate system is set according to the measurement result. Thereafter, reflecting targets (including target points) provided at the individual measuring points are sighted to synchronously measure the three elements, i.e., the horizontal angle, the vertical angle, and the distance. Then, the system performs a coordinate system transformation including analysis and calculations, and obtains a 3-D coordinate according to the transformation. The system is capable of achieving a high-precision measurement with an error of xc2x11 mm or less per distance of 100 m. The target point is provided on a reflection plane, and is used as a measurement point in the 3-D coordinate measurement. A reflecting target has a specific thickness. As such, predetermined calculations need to be performed according to measurement values and the size and shape of the reflecting target to obtain accurate 3-D coordinates of the target object.
However, conventional measuring systems including the xe2x80x9cMONMOSxe2x80x9d require use of the human eye to perform, for example, telescope focusing operation and alignment operation between the center (target point) of a reflecting target and cross lines of the telescope in sighting operation. As such, time-consuming complex operations need to be performed, and human errors of a measuring person tend to be included in measurement results. That is, required human operations causes deterioration in, for example, the efficiency and the precision of the measurement. The aforementioned sighting operation refers to the operation of aligning an optical axis of a distance-measuring device to a measurement point projected in a viewfield of, for example, a telescope or magnifying display means for a captured image.
To overcome the above-described problems, there are commercially marketed measurement systems including functions of automating human-eye dependent sighting operation. For example, a brand xe2x80x9cTCA1100xe2x80x9d series is marketed by Leica Geosystems Corp., and a brand xe2x80x9cCYBER MONMOSxe2x80x9d is marketed by Sokkia Co., Ltd. Either of the systems includes image capturing means, such as a CCD camera, provided concentric with the optical axis of an electrooptical distance-measuring device. The system is so designed as to detect a central position of a reflecting target from an image captured by the image capturing means. Then, the system performs calculations and thereby obtains the amount of deviation between a central position of the image capturing means and the central position of the reflecting target. When the system finds the positions misaligned, it controls a motor to drive an angle measuring device by an amount corresponding to the amount of the deviation, and aligns the positions with each other. The system of the aforementioned type executes automatic sighting (automatic microscopic sighting) within a relatively narrow viewfield of the image capturing means. In this view, the system can be included in a type that has a microscopic automatic sighting means.
In addition, in the aforementioned system, conditions for the positions of reflecting targets and the measurement sequence thereof are initialized. Thereafter, reflecting targets captured by the image capturing means are extracted by an image processor. Subsequently, the horizontal angle and the vertical angle of the image capturing means are adjusted using a servomotor to align the center of each of the reflecting targets with the optical axis of the image capturing means. In this manner, the measurement is implemented. In this case, the reflecting targets need to be included into the viewfield of the image capturing means. As such, difficulties arise in that the plurality of measurement points (target points) in a wide range are automatically sighted. As such, with this system, when a coordinate of the position of a reflecting target is memorized, an operator needs to directly input the coordinate of the position of the reflecting target from a measurement apparatus according to design data. In contrast, when a coordinate of the position of a reflecting target is not yet memorized, the operator needs to direct the image capturing means manually or by using a controller toward the reflecting target to carry out teaching for the system.
Other methods of performing automatic measurement are proposed under, for example, Japanese Unexamined Patent Application Publications No. 8-136218 and No. 9-14921. In the proposed methods, an analysis-dedicated computer is used to transform the position of a reflecting target into a coordinate from a measuring apparatus. Thereby, the sight direction is determined, and automatic measurement is performed.
However, the methods of the above-described type have problems described below.
When a 3-D coordinate of reflecting targets is not yet memorized, teaching needs to be carried out in the way that a CCD camera is directed to individual measuring points, and the operation of including the individual measuring points into a monitor screen is iterated. Thus, since complex human operations are involved, advantages in automation cannot be expected.
Even when 3-D coordinates of reflecting targets are already memorized to the system, although an analysis-dedicated computer is used to transform the coordinate system, time-consuming human operations are required. That is, the method still requires the operation of aligning a design coordinate system and a measurement coordinate system to be performed in the initialization in the way of measuring at least two points of a reflecting target used for reference.
Moreover, although there are cases in which the method is used to position component members in assembly work, the method requires a relatively long time for measurement. In most cases of assembly work, component members are located in positions deviating from the viewfield of the image capturing means. As such, even when the position of a reflecting target is calculated from design values, since the reflecting target is not found in the viewfield, and a reflecting target needs to be searched from the outside of the viewfield. Consequently, it takes a relatively long time for measurement.
Since the performance of the conventional 3-D coordinate measuring method is as described above, it is difficult to directly use the method in assembly work, for example, shipbuilding assembly work.
Recently, most of shipbuilding methods employ a block-based fabrication method. As shown in FIG. 17, in a shipbuilding method, first, processes such as cutting and hot bending are performed for steel plates (material-processing step). Then, processed steel plates are welded and assembled, and intermediate-and-small blocks are thereby fabricated (a step of the above processing will be referred to as an intermediate-and-small block fabricating step). Intermediate-and-small blocks individually fabricated as described above are assembled and welded together, and a large block (which hereinbelow will be referred to as a 3-D block) is thereby fabricated (a step of the above processing hereinbelow will be referred to as a large-assembly fabricating step or a large-block fabrication step). Large blocks individually fabricated as described above are assembled together in a dock (a step of the above processing hereinbelow will be referred to as an intradock assembly step). Thereby, a hull is finally fabricated.
In the above-described shipbuilding method, when the precision in the assembly of the intermediate-and-small block or the large block is low, correction needs to be performed in a subsequently step. xe2x80x9cCorrectionxe2x80x9d in this case refers to a series of the following processes. When the shapes of two blocks to be assembled together do not match, a portion of welded steel plates or members in one or two of the blocks is removed though, for example, gas-cutting, correction is performed to so that the shapes of the two blocks to the shapes of the two blocks are matched, and the removed portion of the steel plates or the member is attached again.
In the shipbuilding process, attaching and welding processes of the steel plate and blocks largely account for the man-hour ratio. As such, an important key for improving the productivity is how to improve the processing efficiency. However, according to the conventional techniques, since the shape precision is only in a range of several tens millimeters, many events requiring the correction have occurred, thereby hindering improvement in the processing efficiency. In addition, defects in the precision of the blocks accumulate as the material-processing step proceeds. Accordingly, when an event requiring the correction occurs at a final intradock assembly step, the correction requires several times the work time required for the corrections event in the previous step, thereby greatly influencing the productivity. Thus, the improvement in the productivity in the shipbuilding process greatly depends on the improvement in the block-shape precision management level in the intermediate-and-small block fabricating step and the large-block fabrication step. According to the improvement in the block-shape precision from a level of several tens millimeters to a level of several millimeters, the overall man-hours for attaching and welding including correction is estimated reducible by several tens percent.
Conventionally, there are other cases in which shape measurement was attempted during an assembly step to improve the precision in the block shape precision. However, according to the conventional 3-D coordinate measuring methods, it takes excessive time to carry out the measurement, and an excessive measurement load therefore occurs. As such, the method is not better than a trial method; that is, the method is not as yet practical.
The present invention has bee developed in consideration of the above-described situations. Accordingly, an object of the invention is to provide a three-dimensional (3-D) coordinate measuring method and a 3-D coordinate measuring apparatus that almost do not require human operations and that are capable of implementing high-speed, high-precision, and substantially automatic measurement of 3-D coordinates even for a large structure even when the coordinates and the like of the positions of reflecting targets are not yet memorized.
Another object of the invention is to provide a large-structure building method that almost does not require human operations, that is capable of implementing high-speed and high-precision automatic measurement of the positions of a plurality of reflecting targets mounted to component members, and that is capable of implementing high-efficiency and high-precision assembly of the component members by using the results of the measurement.
In order to achieve one of the objects, according to one aspect of the invention, the invention provides a three-dimensional (3-D) coordinate measuring method is provided wherein an electrooptical distance-measuring device is used to measure a linear distance to a coordinate-measurement target point set on a surface of a measurement target object, an angle measuring device is used to measure shifted angles of an optical axis of the electrooptical distance-measuring device, and a 3-D coordinate of the target point is measured according to a measured distance and a measured angle after the optical axis of the electrooptical distance-measuring device has been aligned to the target point set on the surface of the measurement target object. The three-dimensional (3-D) coordinate measuring method includes a coordinate recognizing step for observing a plurality of targets on the overall surface of the measurement target object through an image capturing means, recognizing a plurality of target points on the surface of the measurement by processing obtained images, and calculating approximate 3-D coordinates of the target points; a macroscopic sighting step for approximate aligning the optical axis of the electrooptical distance-measuring device so that one of the target points recognized by the coordinate recognizing step is included into a predetermined viewfield range; and a microscopic sighting step for aligning the optical axis of the electrooptical distance-measuring device, which has been approximately aligned at the macroscopic sighting step, to the one of the target points in the predetermined viewfield range.
According to another aspect of the invention, to implement the above-described method, a 3-D coordinate measuring apparatus is provided that includes an electrooptical distance-measuring device for measuring a linear distance to a coordinate-measurement target point set on a surface of a measurement target object; an optical-axis driving mechanism to which the electrooptical distance-measuring device is mounted and that rotates on two different axes as the centers to cause the direction of an optical axis of the electrooptical distance-measuring device to be variable along a horizontal direction and a vertical direction; an optical-axis-angle measuring device for measuring the optical-axis angle of the electrooptical distance-measuring device; a microscopic automatic sighting mechanism for using the optical-axis driving mechanism to align the optical axis of the electrooptical distance-measuring device to the target point in a predetermined viewfield for one target point on the surface of the measurement target object; an image capturing mechanism for observing a plurality of targets set on the overall surface of the measurement target object; a macroscopic-position recognizing means for processing an image obtained by the image capturing mechanism, thereby recognizing a plurality of target points on the surface of the measurement target object, and calculating approximate 3-D coordinates of the target points; a macroscopic automatic sighting mechanism for approximately aligning the optical axis of the electrooptical distance-measuring device so that one of the target points recognized by the macroscopic-position recognizing means is included into the predetermined viewfield; sight control means for using the macroscopic automatic sighting mechanism to align the optical axis to a target point, which has been approximately aligned into the predetermined viewfield of the electrooptical distance-measuring device, of the one target set on the measurement target object and that has been recognized by the macroscopic automatic sighting mechanism; and coordinate calculating means for calculating a 3-D coordinate of the target point by using the results of measurement performed by the electrooptical distance-measuring device and the optical-axis-angle measuring means.
According to still another aspect of the invention, a large-structure building method is provided wherein a plurality of first component members of one or more types are assembled, and a second component member is thereby fabricated; a plurality of the second component members of one or more types are assembled, and a third component member is thereby fabricated; similarly, a plurality of n-th component members of one or more types are assembled, and an (n+1)-th component member are thereby fabricated; and one of an intermediate structure and a final structure is thereby fabricated. The large-structure building method includes a measuring step for automatically measuring real shapes of the n-th component members in a manner that calculating individual 3-D coordinates corresponding to a plurality of coordinate-measurement target points set on the n-th component members are calculated according to distance measurement values of an electrooptical distance-measuring device and information on the angle of an optical axis of the electrooptical distance-measuring device; an evaluating step that evaluates assembly precision of the (n+1)-th component member according to the real shape measured at the measuring step and that issues an instruction for use of only n-th component members usable for assembly of the (n+1)-th component member; a coordinate recognizing step that uses image capturing means to observe targets including a plurality of target points set on the n-th component member and that processes obtained images and thereby recognizes approximate 3-D coordinates corresponding to the plurality of target points set on the n-th component member, the coordinate recognizing step being performed to enable the measuring step to obtain the distance measurement values of the electrooptical distance-measuring device and information on the angle of the optical axis of the electrooptical distance-measuring device; a macroscopic sighting step for approximate aligning the optical axis of the electrooptical distance-measuring device by using the approximate 3-D coordinates so that certain one of the target points recognized by the coordinate recognizing step is included into a predetermined viewfield range; a microscopic sighting step for aligning the optical axis of the electrooptical distance-measuring device, which has been approximately aligned at the macroscopic sighting step, to the certain one of the target points in the predetermined viewfield range; and a step of repeatedly performing the macroscopic sighting step and the microscopic sighting step until the distance measurement value of the electrooptical distance-measuring device and information on the angle of the optical axis of the electrooptical distance-measuring device are obtained for all the target points.